There are a number of insert devices designed to be inserted within a pressurized system. Exemplary insert devices may include pressure relief devices, such as valves and rupture disks. Pressure release devices may be configured to allow pressurized fluid to vent from one part of a pressurized system in response to a dangerous over-pressure situation. Other exemplary insert devices include sensors and measuring equipment. Typically, an insert device may be installed into a pressurized system between two companion flanges, which are held together by way of flange bolts.
In the field of pressurized systems, a number of different flange bolting patterns exist for pipes of a given nominal size. By way of example, for pipes of a given nominal size, different bolting patterns may be required by each of the standards required by the American National Standards Institute (“ANSI”), American Society of Mechanical Engineers (“ASME”), Deutsches Institut für Normung (“DIN”), and Japanese Industrial Standards (“JIS”). Additionally, for pipes of a given nominal size and/or standard, different bolting patterns are required for different pressure ratings. Therefore, it is desirable for an insert device to fit interchangeably within pressurized systems having a variety of flange bolting patterns.
An insert device's performance depends on two principal factors: proper alignment within a pressurized system and proper sealing within a pressurized system. First, if the insert device is a rupture disk, for example, it is desirable for the rupture disk to be aligned as close as possible to the center of the fluid flow path of the pressurized system. Centering or aligning the rupture disk stabilizes flow resistance (Kr) when the rupture disk ruptures, which desirably increases (or otherwise optimizes or stabilizes) the rate at which an over-pressure fluid may exit the system. Second, for any insert device, a proper seal will prevent fluid from leaking into the environment.
One type of insert device achieves proper alignment through the use of a flange adapter. The insert device may align with a flange adapter, which in turn is configured to align with a set of flange bolts. Optimally, a flange adapter is configured to fit a number of bolt configurations for the same nominal size pipe. One flange adapter providing this feature is illustrated in co-owned U.S. patent application Ser. No. 10/936,761, the entire contents of which are incorporated herein by reference.
Known flange adapters may present disadvantages when sealed within a pressurized system. The quality of a flange adapter's seal depends largely on the torque values applied to the flange bolts. An installer may lack the tools or expertise to provide an optimal torque to the flange bolts; therefore, in practice many insert devices may provide less than optimal sealing as a result of improper installation. Additionally, the seal of a flange adapter may depend on the alignment of the companion flanges between which it is installed. For example, factors such as the perpendicularity, parallelism, and concentricity of mating surfaces may influence the sealing arrangement between an insert device (e.g., rupture disk) and its holder, as well as the sealing arrangement between the holder and the companion flanges. In practice, two companion flanges rarely align precisely with each other. A flange adapter or insert device installed between such misaligned flanges may not provide an optimal seal.
Another type of insert device may be installed into a pressurized system with the help of a support apparatus or a safety head assembly. A support apparatus may include an inlet support member and an outlet support member. Assembly bolts hold the two support members together, with the insert device between them. The support apparatus and insert device are mounted between two companion flanges that are joined together with a set of companion flange bolts. The support apparatus may be configured to align an insert device positioned properly between the flange bolts. Additionally, the support apparatus may fit interchangeably within sets of flange bolts corresponding to different pressure rating and design standards, especially for pipes having the same nominal size. One exemplary support apparatus is disclosed in co-owned U.S. Pat. No. 4,751,938 (“the '938 patent”), the entire contents of which are incorporated herein by reference.
In practice, two support members often align with each other more precisely than two companion flanges. Thus, an insert device installed within the support apparatus may provide a better seal than if it were installed directly between two (potentially misaligned) companion flanges. In order to ensure that an insert device is properly aligned within the support apparatus, the support apparatus may be provided to an end user in a pre-assembled configuration. When pre-assembled, the support members are bolted together loosely with an insert device positioned properly between them. Thus, an end user need only install the pre-assembled apparatus between two companion flanges. The insert device in a pre-assembled configuration is sealed within the apparatus and pressurized system by the torque applied to the flange bolts.
A known support apparatus may be made of high-cost wetted materials. A high-cost material may be chosen because of its temperature stability, corrosive resistance capability, and magnetic permeability. Because of material expense, it may be desirable to reduce the amount of material used.
A support apparatus may also provide a better seal if provided to a user in a pre-torqued configuration. When pre-torqued, the assembly bolts of the support apparatus are provided with the optimal level of torque to seal the insert device within it. This optimal level of torque may be applied by a vendor or manufacturer, or by the user before mounting the support apparatus and insert device to an application. When the pre-torqued support apparatus is then installed between two companion flanges of a pressurized system, the insert device's seal is substantially independent of the torque levels applied to the flange bolts. Thus to get an optimal seal, an end user need not possess the skills or expertise to apply a precise torque level to the flange bolts.
Known support apparatus lack the feature of keeping the support apparatus's assembly bolts visible or adjustable after installation. One example of a support apparatus includes assembly bolts that extend vertically through one support member and into another, through a set of through-holes. These through-holes may be countersunk, counter-bored, or provided with any other recess (machined or otherwise) which obscures the assembly bolts. As illustrated in FIG. 3 of the '938 patent, the support members may sit substantially flush with each other. This configuration prevents a user from viewing the threaded portion of any assembly bolts between the support members. Thus, a user cannot verify the presence of assembly bolts within an installed support assembly, when such verification might indicate that the support assembly was installed correctly. Also as illustrated in FIG. 3 of the '938 patent, the companion flange members may completely cover the top and bottom surfaces of the support assembly, thereby preventing a user from seeing or accessing the assembly bolts' heads. Thus a user can neither verify the presence of assembly bolts, nor verify or adjust the level of torque applied to the assembly bolts.
A known support apparatus may also present challenges when removing the support apparatus from between companion flanges of a system. For example, the companion flanges cannot easily or safely be moved in a fixed-piping system, or where the piping is heavy as a result of nominal diameter and/or length. Thus, there is a need for a support apparatus that does not require the removal of all companion flange bolts to remove and/or install a support apparatus.
An additional feature missing from a known support apparatus is durability and versatility when used in corrosive or other harsh environments. Often the contents of a pressurized system exhibit very reactive properties and tend to corrode or erode components of the system. The inner bore of an inlet support member may frequently make contact with these contents, which may tend to erode or degrade the inlet support member. To use an inlet support member in such a harsh environment, it must be made of expensive corrosion- and/or heat-resistant material. Additionally, the inlet support member may require frequent replacement as it becomes corroded or eroded.
Another example of known support apparatus may provide a seal to an insert device through the use of a bite seal. A bite seal includes a ridged portion configured to cut or “bite” into an insert device when the components of a support assembly are pressed together. A bite seal is more effective than a seal depending solely on the pressure applied to an insert device. A known support apparatus provides a bite seal as an integral part of one of the support members. This configuration suffers from numerous disadvantages. First, in some support apparatus, the bite seal must be made of very hard and very expensive materials. When the bite seal is integral with a support member, the entire support member must be made out of the very hard and very expensive material, which increases material cost of the support apparatus. Additionally, a bite seal may suffer from damage through shipment, installation, or repeated use. Such damage may take the form of dents or dings. A damaged bite seal provides an inferior seal with an insert device; therefore, a damaged bite seal should be replaced. In known apparatus, to replace the bite seal requires replacing the entire support member, which increases the cost of maintaining the support apparatus.
In light of the foregoing, there is a need for a support apparatus or safety head assembly that may reduce the use of materials, while retaining or improving upon the functionality of a known support apparatus or safety head assembly. There is also a need for a support apparatus or safety head assembly that facilitates proper alignment and sealing of an insert device within a pressurized system. There is also a need for a safety head assembly that allows assembly bolts to be seen and adjusted while the safety head assembly is installed within a pressurized system. Additionally, there is a need for a safety head assembly having increased resistance to erosion or corrosion at decreased material cost. There is also a need for a safety head assembly having a bite seal that can be replaced at low cost. Further, there is a need for a method of installing and adjusting a safety head assembly that provides improved alignment and sealing.